Bone formation in ankylosing spondylitis during anti-tumour necrosis factor therapy imaged by 18F-fluoride positron emission tomography

Rheumatology (Oxford). 2018 Apr 1;57(4):631-638. doi: 10.1093/rheumatology/kex448.


Objectives: Excessive bone formation is an important hallmark of AS. Recently it has been demonstrated that axial bony lesions in AS patients can be visualized using 18F-fluoride PET-CT. The aim of this study was to assess whether 18F-fluoride uptake in clinically active AS patients is related to focal bone formation in spine biopsies and is sensitive to change during anti-TNF treatment.

Methods: Twelve anti-TNF-naïve AS patients [female 7/12; age 39 years (SD 11); BASDAI 5.5 ± 1.1] were included. 18 F-fluoride PET-CT scans were performed at baseline and in two patients, biopsies were obtained from PET-positive and PET-negative spine lesions. The remaining 10 patients underwent a second 18F-fluoride PET-CT scan after 12 weeks of anti-TNF treatment. PET scans were scored visually by two blinded expert readers. In addition, 18F-fluoride uptake was quantified using the standardized uptake value corrected for individual integrated whole blood activity concentration (SUVAUC). Clinical response to anti-TNF was defined according to a ⩾ 20% improvement in Assessment of SpondyloArthritis international Society criteria at 24 weeks.

Results: At baseline, all patients showed at least one axial PET-positive lesion. Histological analysis of PET-positive lesions in the spine confirmed local osteoid formation. PET-positive lesions were found in the costovertebral joints (43%), facet joints (23%), bridging syndesmophytes (20%) and non-bridging vertebral lesions (14%) and in SI joints (75%). After 12 weeks of anti-TNF treatment, 18F-fluoride uptake in clinical responders decreased significantly in the costovertebral (mean SUVAUC -1.0; P < 0.001) and SI joints (mean SUVAUC -1.2; P = 0.03) in contrast to non-responders.

Conclusions: 18F-fluoride PET-CT identified bone formation, confirmed by histology, in the spine and SI joints of AS patients and demonstrated alterations in bone formation during anti-TNF treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antirheumatic Agents / therapeutic use*
  • Biopsy
  • Female
  • Fluorodeoxyglucose F18 / pharmacology*
  • Follow-Up Studies
  • Humans
  • Imaging, Three-Dimensional
  • Male
  • Middle Aged
  • Osteogenesis / physiology*
  • Positron Emission Tomography Computed Tomography
  • Radiopharmaceuticals / pharmacology
  • Spine / diagnostic imaging*
  • Spondylitis, Ankylosing / diagnostic imaging*
  • Spondylitis, Ankylosing / drug therapy
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors*
  • Young Adult


  • Antirheumatic Agents
  • Radiopharmaceuticals
  • Tumor Necrosis Factor-alpha
  • Fluorodeoxyglucose F18